The present invention relates generally to failure recovery methods for ink-jet printheads that automatically recovers multiple printheads from an ink-clogged condition. More particularly, the invention concerns such a method and system that include automatically capping and selectively priming a printhead to draw dried ink or other contaminant therefrom in response to a detected failure condition of the printhead.
Ink-jet printhead nozzles commonly become plugged with wet or dry ink blobs or foreign matter, or become contaminated with internal bubbles that prevent them from operating properly. Lower print quality and user complaints often result. Even if the user discovers the problem, there often is nothing that can be done short of calling customer service. In a busy printer installation, such can be very costly, in lost opportunity due to excessive downtime, as well as in customer dissatisfaction.
Previously, single printhead systems have been proposed in an attempt to solve the problems of nozzle plugging or bubble formation therein. Typically, such systems require substantial operator intervention, and are not automatic. Further, they typically do not flush the vicinity of the printhead after priming, thereby leaving primed ink to accumulate-and ultimately to dry again and potentially to cause further clogging-near the printhead. Such conventional solutions do not lend themselves to multiple printhead systems.
Drop detectors have been proposed that are capable of detecting the presence of an ink droplet fired from an ink-jet printhead and any delay associated with its firing. One such drop detector, which is suitable for use with the invented automatic failure recovery method and system, is described in U.S. Pat. No. 5,109,239 entitled "Inter Pen Offset Determination and Compensation in Multi-Pen Ink Jet Printing Systems", which issued Apr. 28, 1992 and is subject to common ownership herewith. The drop detector described therein, which preferably is optical, produces a drop present signal indicative of the presence of an ink droplet traversing a detection window within an ink-jet printer. The drop detector is described as being capable also of measuring the time between a firing pulse that heats a thin-film resistor to fire a drop of ink toward a print medium. From such detection and measurement techniques, a failure condition such as a clogged or partially clogged nozzle of an ink-jet printhead may be detected.
A fully automatic failure recovery method and system are proposed that achieve selected priming and flushing of one of plural capped printheads in response to a detector that indicates the need therefor. The priming duration and pressure are adjustable in accordance with the automatically determined extent of the failure of the selected printhead reliably to fire ink droplets. In its preferred embodiment, the system uses a plural cam and cam follower subsystem that has few moving parts and that is selectively rotated via a one-way clutch with the ink-jet printer's paper feed drive motor. The recovery system cycle time is relatively short, thus minimizing printer downtime and maximizing quality print throughput.
These and additional objects and advantages of the present invention will be more readily understood after a consideration of the drawings and the detailed description of the preferred embodiment.